This new application proposes to investigate a newly identified mechanism of injury in shock which contributes to cellular and organ dysfunction. This PARS pathway of injury is triggered by oxidant-induced DNA single strand breaks. Recognized by the N-terminal domain of the nuclear enzyme poly (ADP-ribose) synthetase (PARS), oxidant-induced genetic damage activates the C-terminal domain of PARS, which catalyzes and energy consuming polymerization of ADP-ribose. Depletion of NAD by this process slows the rate of glycolysis and mitochondrial respiration, and thereby reduces ATP synthesis. In this proposal the applicant plans to test the central hypothesis that the PARS pathway contributes to organ injury and dysfunction in splanchnic I-R injury. 1. He will determine the whether pharmacological inhibition of PARS ameliorates cytotoxicity of cultured intestinal epithelial cells exposed to an in vitro oxidant stress (using nitric oxide, superoxide, peroxynitrite, or anoxia-reoxygenation). 2. He will establish whether PARS activation contributes to mucosal dysfunction in a rodent model of I-R injury. 3. He will establish whether PARS activation imitates a positive feedback cycle of mesenteric vascular injury by testing the effect of. PARS inhibitors on endothelial function in splanchnic I-R injury. The ultimate goal is to determine whether PARS inhibition represents a plausible strategy to prevent and treat splanchnic I-R injury.